A Channel 4 News report at the end of yesterday's 7pm bulletin - based on a freedom of information request - revealed the BBC spent more than £45,000 on the launch party for fantasy drama Merlin and more than £118,000 on three other bashes.

The BBC immediately hit back with a claim that Channel 4 spent around £80,000 on a staff Christmas party last week, although sources at the commercial broadcaster denied the figure, saying the cost was more like £40,000.

Although the bitching between the two broadcasters was over something relatively minor - after all, all the main channels host programme launch events and throw Christmas parties - the spat has more relevance when placed against the increasingly bitter backdrop of the two players' differences over the future direction of public service broadcasting.

The BBC is desperate not to have to hand over all or part of its commercial arm BBC Worldwide - or a slice of the licence fee - to Channel 4, while the commercial broadcaster is desperate to secure additional money - or other practical forms of assistance - to plug what it claims will be a £150m annual funding gap by 2012.

Channel 4 News's decision to devote airtime to the cost of BBC launches - a rare unprovoked criticism of a rival's operating practises - surprised many, not least executives at the commercial broadcaster, with insiders keen to point out that the Channel 4 chief executive, Andy Duncan, had no prior knowledge of the item.

The FoI request, which would have been submitted several weeks ago, found that the BBC spent £45,572 in September on a party for 326 people at London's Oxo Tower to celebrate the launch of Merlin.

According to the BBC, the figure included food, beverages, room hire, photography, security, entertainment, invitations, transport and production, with the guests including "11 BBC staff working in areas such as production" as well as "members of the media, cast, and key crew, directors, actors, presenters, community representatives and opinion formers".

Now, as a matter of disclosure, I was one of the guests at the bash, which followed a screening of the first episode of Merlin at the Imax theatre.

It is par for the course for broadcasters to promote big new shows with parties for journalists and this was no exception, although the setting was probably a little more extravagant than normal.

At more than £45,000, industry insiders have said this is more expensive than usual programme launches because it was aimed at "opinion formers" such as MPs and not just press.

However, it was cheap compared with the amounts previously spent by all the big broadcasters - including the BBC and Channel 4 - on digital channel launches, with industry insiders saying these bashes can easily cost between £100,000 and £150,000 and even as much as £250,000. I was at a lot of them and can attest to the extravagence.

Regular programme screenings on the other hand can come in at between £7,000 and £10,000.

For big launches, the BBC has a special corporate events department that has a standalone annual budget of several million pounds, although like all areas at the corporation this has had to cut costs in recent years.

The BBC has said it has cut down on the number of launches it undertakes and will do so further next year.

Hitting back at the Channel 4 News claims yesterday evening, BBC insiders pointed the finger at Channel 4 itself, saying it had shelled out thousands of pounds on a party for staff at the Pasha nightclub in London.

The commercial broadcaster defended itself by saying it had paid the deposit in May - before the most recent economic crash - and had left it up to staff to decide whether it should back out or go ahead with the bash. Unsurprisingly, the staff chose to go ahead.

When it comes to spending money on parties, the BBC has more to answer for as it is paid for by the licence fee, while Channel 4, despite also being state owned, is a commercial entity.

However, the further negative publicity Channel 4 has helped generate for the BBC over this incident should be a salutary lesson for the commercial broadcaster itself. For if it succeeds in getting its hands on BBC money or assets, Channel 4 could soon find the spotlight of increased scrutiny shining on it.